From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: qemu-kvm requires apic initialized before vcpu main loop Date: Wed, 9 Dec 2009 18:09:26 -0200 Message-ID: <20091209200926.GB28264@amt.cnet> References: <20091209174654.GA28056@amt.cnet> <20091209182545.GO30411@mothafucka.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , Glauber de Oliveira Costa , kvm To: Glauber Costa Return-path: Received: from mx1.redhat.com ([209.132.183.28]:62411 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757634AbZLIUOM (ORCPT ); Wed, 9 Dec 2009 15:14:12 -0500 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id nB9KEI5F018429 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 9 Dec 2009 15:14:19 -0500 Content-Disposition: inline In-Reply-To: <20091209182545.GO30411@mothafucka.localdomain> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Dec 09, 2009 at 04:25:45PM -0200, Glauber Costa wrote: > On Wed, Dec 09, 2009 at 03:46:54PM -0200, Marcelo Tosatti wrote: > > > > Otherwise a zero apic base is loaded into KVM, which results > > in interrupts being lost until a proper apic base with enabled > > bit set is loaded. > > > > Fixes WinXP migration in qemu-kvm origin/next. > > > > Signed-off-by: Marcelo Tosatti > > > > diff --git a/hw/apic.c b/hw/apic.c > > index 627ff98..45a4d2b 100644 > > --- a/hw/apic.c > > +++ b/hw/apic.c > > @@ -1131,6 +1131,11 @@ int apic_init(CPUState *env) > > vmstate_register(s->idx, &vmstate_apic, s); > > qemu_register_reset(apic_reset, s); > > > > + /* apic_reset must be called before the vcpu threads are initialized and load > > + * registers, in qemu-kvm. > > + */ > > + apic_reset(s); > > + > But by doing this, the system-wide reset will re-reset the apic, possibly losing > some other information. The information is the same. vcpu did not run (so did not change any information) between apic_reset and system wide reset. > Also, system_reset happens before we signal system_ready (or at least should). Not in qemu-kvm.c. Even if it did, it is too late (by that time vcpu thread will have loaded APIC base of 0). qemu-kvm.c should be updated to call system_reset, I believe, similarly to what has been done to vl.c. > This means the vcpus should not be running and producing anything useful yet. > So how does it happen, in the first place? The initialization of env->apic_base must happen before the vcpu thread calls kvm_arch_load_regs in qemu-kvm.c. Otherwise the vcpu thread initializes env->apic_base with value of "0", and that in turn will result in the kernel's "apic_hw_enabled()" returning false, so interrupt injections in that period are lost, for one problem. Its similar issue that this comment on hw/pc.c refers to: /* kvm needs this to run after the apic is initialized. Otherwise, * it can access invalid state and crash. */ qemu_init_vcpu(env); return env;